A device for sharpening taps is known from U.S. Pat. No. 3,722,148. This arrangement can be set up to displace a tool-holder through an eccentric path. The tap is mounted in a collet in the holder and can be appropriately positioned with respect to a grinding wheel to refinish the end of the tap. Under normal circumstances the tap end only needs to be refinished, as it is only this portion of the tool which is subjected to any appreciable wear.
This device has several considerable disadvantages. It requires a separate collet for each size of tap, to center it in the holder. The expense involved in providing all these collets is considerable, in particular as they must be meticulously machined to close tolerances. What is more, it is only possible to sharpen standard taps with the device. A tap whose angular relief varies from the standard one cannot be refinished with such an apparatus. The eccentricity of the tool-holding sleeve is fixed, so that the usefulness of the device is rather limited.